Method for producing polarizer

Abstract

A method for producing a polarizer ( 20 ) comprises the steps of: (A) stretching a polyvinyl alcohol-based resin layer ( 10 ) to obtain a stretched layer ( 14 ); (B) immersing the stretched layer ( 14 ) in a dyeing liquid ( 23 ) containing iodine to obtain a dyed layer ( 18 ) in which absorbance thereof determined from a tristimulus value Y is from 0.4 to 1.0 (transmittance T=40% to 10%); and (C) removing a part of iodine adsorbed in the dyed layer ( 18 ) so that the absorbance of the dyed layer ( 18 ) decreases by 0.03 to 0.7, provided that the absorbance of the dyed layer ( 18 ) is controlled so that it does not become less than 0.3.

The invention claimed is:  
     
       1. A polarizer comprising a stretched layer of polyvinyl alcohol-based resin including iodine adsorbed therein;
 wherein said layer of polyvinyl alcohol-based resin has a thickness of 0.4 to 7 μm and includes polymer chains oriented substantially in one direction, said polymer chain including a highly oriented crystallized portion, and said layer of polyvinyl alcohol-based resin surrounding the crystallized portion is amorphous; and 
 wherein said iodine adsorbed in said layer of polyvinyl alcohol-based resin is present in said layer of polyvinyl alcohol-based resin in the form of polyiodine ion complex adsorbed to the crystallized portion of said layer of polyvinyl alcohol-based resin to provide the polarizer with a dichroic property, whereby the polarizer exhibits an absorbance of 0.359 to 0.380 and a polarization degree of 99.9% or higher, and the absorbance is determined based on a Y value of an XYZ colorimetric system as defined by JIS Z 8701. 
 
     
     
       2. The polarizer in accordance with  claim 1  wherein the polarizer exhibits an absorbance of 0.362 to 0.377 and a polarization degree of 99.9% or higher. 
     
     
       3. A polarizer comprising a stretched layer of polyvinyl alcohol-based resin including iodine adsorbed therein;
 wherein said layer of polyvinyl alcohol-based resin has a thickness of 0.4 to 7 μm and includes polymer chains oriented substantially in one direction, said polymer chain including a highly oriented crystallized portion said layer of polyvinyl alcohol-based resin surrounding the crystallized portion is amorphous; and 
 wherein said iodine adsorbed in said layer of polyvinyl alcohol-based resin is present in said layer of polyvinyl alcohol-based resin in the form of polyiodine ion complex adsorbed to the crystallized portion of said layer of polyvinyl alcohol-based resin to provide the polarizer with a dichroic property, whereby the polarizer exhibits an absorbance of 0.377 or less and a polarization degree of 99.95% or higher, and the absorbance is determined based on a Y value of an XYZ colorimetric system as defined by JIS Z 8701. 
 
     
     
       4. The polarizer in accordance with  claim 3  wherein the polarizer exhibits an absorbance of 0.362 to 0.377 and a polarization degree of 99.95% or higher. 
     
     
       5. The polarizer in accordance with  claim 1  wherein said polyiodine ion complex is adsorbed to said crystallized portion of said polymer chain in the form of I 3   −  or I 5   − . 
     
     
       6. The polarizer in accordance with  claim 3  wherein said polyiodine ion complex is adsorbed to said crystallized portion of said polymer chain in the form of I 3   −  or I 5   − .